Bleaching of wheat flour and like milled products



Patented Dec. 30, 1947 BLEACHING OF WHEAT FLOUR AND LIKE MILLED PRODUCTS Bert Dee Ingels, East Orange, N. J.,- assignor to Novadei-Agene Corporation, Believille, .N. J., a corporation of Delaware No Drawing. Application January 15, 1944,

Serial No. 518,448

1 This invention relates to the bleaching of wheat flour and like milled products and in its more 16 Claims. ((199-232) specific aspects to an improved bleach for and method of bleaching flour.

The bleaching properties of certain of the organic peroxy compounds, and in particular of benzoyl peroxide and per-benzoic-acid, have long been known, and flour bieaches containing benzoyl peroxide have enjoyed wide usage. Benzoyl peroxide is usually prepared by peroxidizing benzoyl chloride at C. with hydrogen peroxide or sodium peroxide, or mixtures of the two. Since benzoyl peroxide has a lower specific gravity than the solution in which it is formed, it readily rises to the top as a wet, fiocculent mass. Thereupon, this wet, light benzoyl peroxide is separated from the spent solution, is washed with water and, dried superficially, for example in a centrifugal wringer. When centrifuged as aforesaid, benzoyl peroxide contains from 20 to 30% moisture which according to commercial procedure is subsequently removed by spreading the wet or moist benzoyl peroxide in thin layers on trays and treating with a current of hot air.

In preparing a benzoyl peroxide composition for bleaching fiour, it is customary to mix the dried benzoyl peroxide with an inert mineral compound containing considerable water of crystallization and thereupon to grind this mixture to desired fineness.

In addition to the labor, energy and equipment required in the drying and grinding operations,

both are hazardous due to the fact that benzoyl I peroxide melts at 106 C. with the evolution of heat and explodes violently at temperatures between 106 and 110 C. Moreover, standard methods of flour bleaching which employ dry, powdered benzoyl peroxide are open to the objection that they requir relatively expensive equipment effectively to disseminate the peroxide throughout the flour as is necessary to secure the desired full and uniform oxidizing effect thereof. Furthermore, powder bleaches oi the character indicated increase the ash content of the fiour, and thus their use is objectionable and expensive to those mills which sell flour on ash specification.

Accordingly, the principal objects of the present invention are the provision of a flour bleach and a method of bleaching flour which overcome the above-noted disadvantages and objections to the known bleaching practices and bleaching compounds employed therein; the provision of a benzoyl peroxide bleach which is simple and nonhazardous in its preparation and which can be effectively applied to the flour under treatment without the requirement of expensive equipment;

the provision of a simplified and effectiv flour bleaching method preferably employing benzoyl peroxide as the active bleaching agent, by the practice of which the peroxide may be applied with maximum effectiveness and uniformity throughout the flour being treated; and the pro vision of a simplified method of adding benzoyl peroxide directly to the flour and without the addition thereto of fillers which increase the ash content of the flour.

The improved bleaching composition according to the present invention proceeds in part from my discovery that wet benzoyl peroxide as it comes from the centrifugal wringer and contain ing from 20 to 30% moisture is a perfectly safe product to handle, pack, ship and store, and moreover that benzoyl peroxide is not decomposed by water in the usual warm weather temperatures up to 40 C. nor when it is subjected to freezing temperatures below 0 C. Thus, it is feasible to ship wet benzoyl peroxide to a mill making up its own bleach in water-tight containers such as in the wooden barrels used for lard, whiskey or vinegar, and to store with safety the wet benzoyl peroxide for substantial periods, and without loss of oxidizing strength.

I have also discovered that benzoyl peroxide is highly soluble in carbon tetrachloride and that wet benzoyl peroxide containing 20 to 30% water can be dissolved in either cold or hot carbon tetrachloride, and that the solution thus formed, when separated from the water content of the peroxide which is allowed to separate from the solution and when disseminated throughout wheat and like flours, effects satisfactory bleaching of the'same.

Accordingly, my invention in its broad aspects contemplates a bleaching composition prepared at the flour mill, if desired, by dissolving an organic peroxy compound such as wet benzoyl peroxid containing 20 to 30% water in an organic solvent such as carbon tetrachloride,separating the thus formed solution from the water which is allowed to separate therefrom, and applying the solution tothe flour to be treated in such manner as to obtain thereon the oxidizing effect of the benzoyl peroxide. While the solution as aforesaid may be applied to the flour by various procedures, according to the preferred method, the benzoyl peroxide solution obtained as indicated is by .means of suitable regulating and metering devices and the necessary spray equip-- ment, sprayed on to a minor stream of unbleached fiour taken or divided from the main stream. of

the flour to be treated, the spraying aforesaid being accompanied by agitation. The treated minor stream of flour may then be: passed through an evaporator or aerator, or a combination of the two, to volatilize any excess carbon tetrachloride, the benzoyl peroxid remaining in and the latter, 800 grams of wet benzoyl peroxide.

containing approximately 200 grams of water are dissolved in 15 litres of carbon tetrachloride at a temperature above C. With the water content of the benzoyl peroxide separating out from the solution as an upper layer, the solution is drawn off from under the water layer and is sprayed on to a suitable minor stream of the unbleached flour as aforesaid at the rate of 80 cc. of solution per minute to 10 lbs. of flour per minute, the so treated minor stream'being thereupon returned to a major continuously flowing stream of. 90 bbls. of flour perhour. or course, the foregoing proportions are to be taken as illustrative only, as the amount of benzoyl peroxide to be dissolved in any quantity of carbon tetrachloride, and the amount of such solution required to be sprayed on to a stream of flour or other partially processed stock in a flour mill may and generally will vary between wide limits.

Moreover, the solubility of benzoyl peroxide in carbon tetrachloride increases with the temperature of the latter, so that by dissolving the peroxide in hot carbon tetrachloride I am able to obtain highly concentrated bleaching solutions for the treatment of a particular product requiring the greater oxidizing effect, or to satisfy conditions requiring economy in .the amount of carbon tetrachloride initially used as -well as to reduce recovery losses thereof due to evaporation. To evidence the relative strength or concentrations of the solution obtainable in accordance with the present invention, the following tabulation is set forth:

At 10 deg. C.-4 grams benzoyl peroxide will dissolve in 100 cc. carbon tetrachloride.

At 24.4 deg. C.'l grams benzoyl peroxide will dissolve in 100 cc. carbon tetrachloride.

At 52 deg. C.29 grams benzoyl peroxide will dissolve in 100 cc. carbon tetrachloride.

At 60 deg. C.-44 grams benzoyl peroxide will dissolve in 100 cc. carbon tetrachloride.

As an example of the use of a more highly concentrated solution which may be prepared theabove example. The use of the concentrated,

solution offers the advantage that less than 20 cc. carbon tetrachloride are required to be removed from the middlings by evaporation and/or aeration.

It is also possible, according to the present invention, to combine the maturing effect of carbon tetrachloride on flour, as disclosed in my copending application Serial bid-518,449, filed January 15, 1944 entitled Improvement of wheat and other flours," with the bleaching effect of the benzoyl peroxide, by treating the whole stream of flour with a solution of benzoyl peroxide in carbon tetrachloride, using a weaker solution a greater amount of carbon tetrachloride) than has been indicated in the above two examples. A satisfactory solution giving such a combined bleaching and maturing efiect is prepared by dissolving sufficient wet benzoyl peroxide in a required quantity of carbon tetrachloride so that 1,000 cc. of carbon tetrachloride will contain 4 grams of benzoyl peroxide, and

spraying this solution at the rate of 1,000 cc. per

minute onto 1 bbl. (196 lbs. of flour per minute). The carbon tetrachloride is allowed to remain in contact with the flour until the desired maturing and some bleaching has been efiected, and thereupon the so treated flour is su jected to suitable evaporation and/or aeration to remove the carbon tetrachloride, the benzoyl peroxide being left in the flour to complete its bleaching action.

While the examples set forth above give general indication of the relative strength of the benzoyl peroxide-carbon tetrachloride solution, I .do not limit myself to the amount of carbon tetrachloride to be used in making up a particular solution, because such is not possible in actual milling operation. In general, however, it may be said that smaller amounts of carbon tetrachloride (greater concentration of benzoyl peroxide) would be used in treating the minor flow of flours, thus to cut down recovery losses. Greater percentages of carbon tetrachloride will be employed under conditions requiring a greater dispersion of the benzoyl peroxide throughout the flour and hence a more intimate contact between the peroxide and the flour particles, and also wherelt is desired to obtain the bleaching and maturing action of the carbon tetrachloride. It will be understood. also, that the amount of bleaching and maturing required varies with the wheats used, crop conditions, the locality in the rate of 280 bbls. per hour, r eed ng as in which the wheat is raised, the soil and weather, all of which are factors having material efiect upon the color and baking quality of bread made from flours milled from such wheats. Moreover, thegrade of the flour, the needs and pecularities of the flour used, all greatly affect the amount of benzoyl peroxide and/or carbon tetrachloride that should properly be applied to any given flour for maximum benefits and enhanced qualities of the flour so treated.

From the fore oing it will be appreciated that the above describedbleaching method is one in which the benzoyl peroxide isadded directly to the flour and thus adds nothing to the flour as a mineral filler, as distinguished from prior processes requiring the use of mineral fillers inapplication of the peroxide. As such fillers when added to flours increase the ash, the present method of bleaching is of substantial advantage for those mills which sell flour on ash specifications and towhich the use ,of bleaching powders ,with high ash fillers are accordingly expensive and undesirable. The present method of applying benzoyl'peroxide directly to the flour also satisfies the objections of those nutritionists who question the desirability of the addition of even small amounts of talc (hydrated magnesium carbonate), potash alum (potassium aluminum sulfate), and like fillers to flour, on the ground of the possible undesirable cumulative eifects of eating bread containing such mineral fillers three times per day each day of the year.

However, the invention is not limited to the direct application of benzoyl peroxide to the flour by the above described procedure of spraying a solution of benzoyl peroxide in carbon tetrachloride on flour or on an intermediate streamof middlings or flour in a flour mill, for the reason that I have found that a carbon tetrachloride solution of benzoyl peroxide can 'be applied as by spraying on to mineral powders of the class of calcium salts of a mineral acid which are suitable for use as a flour filler, such as calcium sulfate with 2 mols of water of crystallization or monoor di-calcium phosphate in a suitable mixing device under suitable temperature conditions, thus to provide a bleaching powder for mixture with the flour to be bleached. Such a bleaching powder can be prepared as a stable material in free-flowing form resistant to agglomeration without grinding of the mineral powder along with the peroxide as heretofore and without the necessity for de-lumping or. lump inhibiting agents, such as tale, to keep it from arching or causing feeding clifiiculties in the usual chemical feeders used for such purposes in flour mills.

By way of example of such a bleaching powder, to 37 lbs. of terra alba (calcium sulfate with 2 mols of water of crystallization) at room tempperature and which has been thoroughly sifted, there is sprayed at the rate of 100 cc. per minute a solution of 7 lbs. of benzoyl peroxide in approximately 3'7 lbs. of carbon tetrachloride. The temperature of the powder may be increased if necessary to 45 or 50 C. in order to evaporate the carbon tetrachloride approximately as rapidly as it is added. At the completion of the spraying process, the powder is again sifted through #10 silk bolting cloth and is ready for packaging and shipment to flour mills.

The preparation of benzoyl peroxide powder bleaches as aforesaid is subject of wide variation, both as to concentration of the solution applied to the mineral powder, the temperature of the solution and powder, and also in the mixing procedure including agitation and the rate of the latter. It is also possible and practical to spray the solution onto a cold powder and; when the powder becomes moist, to discontinue the spray and evaporate the carbon tetrachloride, repeating this procedure until the powder flour, farina, or fine middlings, are all suitable for use as diluents for the addition of benzoyl peroxide in a powder form to hour. No grinding is necessary and the presence of carbon tetrachloride renders the production thereof entirely.

safe. I have found that such powders made from defatted farina and defatted starch and containing benzoyl peroxide will keep for four cidity which usually accompanies the addition of more than 1% benzoyl peroxide to amt-bearing food product such as flour.

The above. described procedure also lends itself to the addition of benzoyl peroxide for its oxidizing value to monocalcium phosphate which is used in certain sections of the country as an ingradient of the so-called phosphated and selfrising flours. The proper amount of a solution of benzoyl peroxide can be sprayed on to the phosphate and the carbon tetrachloride evaporated, so that when the usual amount of phosphate- (and sodium bi-carbonate or its equivalent for the'self-rising flours) is added to the flour the desired bleaching effect will be obtained as well. Such procedure will be seen to represent an economy since it eliminates one operation at the flour mill.

While in the foregoing, reference has been made throughout to benzoyl peroxide as the preferred bleaching agent for the reason that thus far none of the other organic peroxides appear to have been used commercially due probably to the difllculty in preparing and thereupon transferring the peroxide to the flour, the invention is applicable to the use of the other organic peroxides as well as organic per-acids and ozonides, which are within the category of known flour-bleaching substances, these substances being generically referred to herein as organic peroxy flour-bleaching compounds or by equivalent terminology.

I claim:

l. A flour bleaching composition, comprising an organic peroxy flour-bleaching compound dissolved in carbon tetrachloride.

A flour bleaching composition, comprising benzoyl peroxide dissolved in carbon tetrachloride.

3. A flour bleaching composition, comprising the product of wet benzoyl peroxide containing 20-30% of water dissolved in carbon tetrachloride, from which the water content of the peroxide has been substantially removed.

4. The method of bleaching flour which comprises treating the flour with an organic peroxy compound dissolved in carbon tetrachloride, and thereupon evaporating the carbon tetrachloride from the so treated flour.

5. The method of bleaching flour which comprises treating the flour with benzoyl peroxide dissolved in carbon tetrachloride, and thereupon evaporating the carbon tetrachloride from the so treated flour.

6. The method of bleaching flour which comprises dissolving benzoyl peroxide in carbon tetrachloride, spraying the resulting solution on to a stream of the flour to be bleached, and thereupon'evaporating the carbon tetrachloride from the so treated flour.

7. The method of bleaching flour which comprises dissolving wet benzoyl peroxide containing 20-30% water in carbon tetrachloride, separating the water content of the peroxide from the resulting solution, spraying the non-aqueous solution on to astream of the flour to be treated.

8. The method of bleaching flour which comprises treating a minor stream of the flour to be treated with a solution of benzoyl peroxide in carbon tetrachloride, evaporating the carbon tetrachloride from the so treated flour, and mixing the treated minor stream with the major stream of the flour to be treated.

9. The method of bleaching and maturing flour until the carbon tetrachloride eflects the desired bleaching and maturing action, and evaporating the carbon tetrachloride while allowing the benzoyl peroxide to continue its bleaching eflect on the flour. 1

10. The method of bleaching and maturing flour which comprises treating flour with a solution of benzoyl peroxide in carbon tetrachloride in the approximate proportion of 4 grams of benzoyl peroxide to 1,000 cc. of carbon tetrachloride and at the approximate treating rate'of 1,000 cc. of solution to one barrel of flour per minute, allowing the carbon tetrachloride to remain on the flour-until its desired bleaching and maturing effect is obtained. and evaporating the carbon tetrachloride while allowing the-benzoyl peroxide to continue its bleaching efiect on the approximately two mols of water of crystallization and monoor di-calcium phosphate, with benzoyl peroxide dissolved in carbon tetrachloride, and.

mixing the so treated powder with the flour to be bleached. f

13. The method of preparing a benzoyl peroxide bleaching composition which comprises dissolving wet benzoyl peroxide containing 20-30% water in carbon tetrachloride, allowing the water content of the peroxide to separate from the solution, and draining ofi the water.

1'4. The method of preparing a benzoyl peroxide bleaching composition which comprises dissolving wet benzoyl peroxide containing 20- 30% water in carbon tetrachloride at a temperature of between 20 C. and C., allowing the water content of the peroxide to settle from the solution. and draining oil. the water.

15. The method of preparing a benzoyl peroxide bleaching composition which comprises spraying benzoyl peroxide dissolved in carbon tetrachloride onto a powdered filler material suitable for addition to wheat and like flours, the temperature of said filler material being sufflcient to evaporate the carbon tetrachloride approximately as rapidly as it is added.

16. The-method of preparing a benzoyl peroxide bleach-composition which comprises spraying benzoyl peroxide dissolved in carbon tetrachloride onto a powdered filler material, suitable for addition to wheat and like flours, to the point of rendering the filler material moist, removing the carbon tetrachloride from said filler material, and repeating the spraying and carbon tetrachloride removal until a predetermined bleaching strength in the powdered material isattained.

BERT DEE INGELS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENdES Gregory, Uses and Applications of Chemicals and Related Materials, Reinhold Publishing Corporation, New York, 1939. 

